假单胞菌N-13中丝氨酸羟甲基转移酶的酶学性质研究

从产L-丝氨酸菌株假单胞菌N-13中纯化了丝氨酸羟甲基转移酶,并对其性质进行了研究.结果表明,丝氨酸羟甲基转移酶酶活力在pH=7.0～9.0间稳定,最适宜pH=8.0;酶的最适温度为35℃,在30～40℃水浴30 min酶活力未见明显下降.磷酸吡哆醛的最适添加浓度为25 μmol·L-1.研究了不同金属离子对酶活力的影...     

几丁质酶产生菌筛选鉴定及产酶性能研究

从土壤样品中筛选得到一株高产几丁质酶菌株C65-2,经形态学观察和18S rDNA序列测定,鉴定为Aspergillus fumigatus,对产酶培养基进行初步优化,测得最高酶活可达6.9U/ml,酶活力较优化之前提高了210%。酶学性质研究表明该几丁质酶分子量约为20kDa,酶在60℃下保温50min酶活降为0,最适酶反应温度是55℃,酶反应最适pH为7.0,Mg2+,Cu2+对酶反应有促进作用,Fe3+对酶反应有抑制作用。     

接枝淀粉载体固定化糖化酶的研究

合成了淀粉接枝丙烯腈及丙烯酰胺的两亲性高分子化合物,并以此为载体,用物理吸附方法固定化了糖化酶。最适偶联条件研究表明：缓冲液的浓度,ｐＨ值及吸附时间和加酶量都对固定化酶活力,比活有一定的影响。在最适固定化条件下,固定化酶的活力为１５００Ｕ／ｇ干胶,蛋白载量为２５ｍｇ／ｇ干胶,比活为６０Ｕ／ｍｇ蛋白,比天然酶的比活（８．０Ｕ／ｍｇ蛋白）提高６倍。最适反应温度比天然酶提高１０℃（天然酶最适反应温度为５０℃）．无底物存在下,固定化酶在５５℃的半衰期为２４ｈ,而天然酶只有１ｈ;有底物存在下,固定化酶在５５℃的半衰期为２２０ｈ,４５℃的操作半衰期由外推法算得为６９天,而且该载体对糖化酶有一定的保护作用,当固定化酶在低于５５℃热处理一段时间后,对酶活力有激活作用,酶活力最大可提高４０％。该载体合成简单,固定化方法简单,步骤少,因而为工业上应用提供了一种新的可能性。     

链霉菌Strz-6木聚糖酶的纯化和固定化研究

链霉菌胞外木聚糖酶经过盐析、离子交换和分子筛层析纯化,粗酶液被纯化了32.5倍,比活力达498u/mg,活力回收46.6%。纯化后的酶固定在戊二醛交联的壳聚糖上,酶活回收率为42.8%。固定化酶的最适pH为6.0,最适温度为60℃,且固定化酶在65~75℃活力都较高。该酶的耐热性比较强,固定化酶热稳定性优于原酶;以木聚糖为底物,固定化酶的表观米氏常数为0.93×10-2g/L。     

产木聚糖酶菌株的选育及其液体发酵条件

从土壤中筛出一株生长快产木聚糖酶活力较高的黑曲霉(Aspergillus niger)C—2菌株,经紫外线和甲基磺酸乙酯诱变,获得一突变株An—76,其生长减缓,孢子形成能力减弱,产生的术聚糖酶和β—木糖苷酶活力分别可达353．61U／ml和4．51U／ml。测定了An—76的正常产酶曲线,研究了麸皮、氮源、碳源及半纤维素浓度对产酶的影响。最适培养条件为：起始pH6.0、28℃、96h。酶的最适作用条件为50—55℃,pH4．8,在pHl．2—11．4范围内稳定。酶的热稳定性较差,55℃保温1小时,剩余活力为40％。只有在含木糖苷类物质存在时,An—76才大量合成木聚糖酶。     

黑曲霉纤维素酶的纯化及酶学性质研究

黑曲霉(Aspergillusniger)固态发酵后粗酶液经硫酸铵盐析,2次SephadexG-200柱层析后可提纯8倍左右.CMC酶最适作用温度为60℃,最适作用pH为3.5,30℃～70℃区间酶活力较稳定,在pH3.0～5.0范围内,50℃保温30min能保持80%的酶活力.CMC酶的Km、Vmax值分别为7.69%CMCg/ml、0.33mg/ml·     

一组厌氧真菌菌系产阿魏酸酯酶的初步研究

利用玉米秸秆粉为唯一碳源的筛选培养基,从肉牛瘤胃液中筛选构建了一组厌氧真菌菌系,研究了该菌系产阿魏酸酯酶的特征.阿魏酸酯酶的最适pH为8.0,最适温度为40℃,最高酶活力为19.1 mU/mL,在pH 6.0 ～8.0及35～45℃之间,酶活性保持相对稳定.Mg2+对酶活力具有激活作用,Fe2、Cu2+、Fe3+等均抑制酶活力.     

烟色红曲霉耐热解脂酶的形成及特性

烟色红曲霉(Monacus fulginosus)M-101菌株经麦麸固态培养生成耐热脂肪酶和酯酶。产酶的适宜条件为:培养温度30℃,初始pH 3.0—3.5,麸曲初始含水量75％。培养4—5天后,脂肪酶活力可达207u/g,酯酶活力达14.6u/g。粗酶试验表明,脂肪酶和酯酶的最适反应温度为50℃,脂肪酶最适反应pH为6.0。酯酶最适反应pH为6.8。酯酶耐热性略高于脂肪酶,在55℃处理1小时和45℃处理24小时,两种酶活力基本不变。     

木霉GXC产β-葡聚糖酶条件和酶学性质

研究了木霉GXC产β-葡聚糖酶的条件.结果表明,最适产酶碳源为麸皮,氮源为硫酸铵;产酶的最适条件为初始pH为4.0～5.0,30℃培养44h.粗酶液经硫酸铵沉淀、Sephadex G-25、Sephadex G-100和DEAE-Sehadex A-50柱层析得到纯β-葡聚糖酶,SDS-PAGE凝胶电泳显示一条带,测得分子量为35kD.该酶最适反应pH5.0,最适反应温度为60℃,在40℃以下、pH4.0～5.0酶活力相对稳定.5.0mmol/L以下的Ca2+、Zn2+和Fe2+,以及10.0mmol/L以下的Co2+对酶活力有激活作用;而Cu2+和Fe3+具有抑制作用.     

黑曲霉A3菌株木聚糖酶粗酶制剂的制备和性质

本文研究了黑曲霉（AspergillusnigerA3）菌株固体发酵培养的产酶过程,发酵3d产木聚糖酶活最高,固体曲最适浸提比为1：7（W／V）,通过60％～65％饱和度的硫酸按盐析,获得的木聚糖酶活力最高。冻干酶粉活力为15400u/g,得率为71％,40℃烘干酶粉活力为15395U／g,得率为51％,酶反应最适温度55℃,最适pH4．6,保温1h半失活温度（t1／2）为54℃,酶对四种不同底物半纤维素水解作用的亲合性为鼓皮最强,稻草最弱。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.